The Collaborative International Dictionary of English v.0.48:

Filmy \Film"y\, a.
   Composed of film or films.
   [1913 Webster]

         Whose filmy cord should bind the struggling fly.
                                                  --Dryden.
   [1913 Webster]

WordNet (r) 3.0 (2006):

filmy
    adj 1: so thin as to transmit light; "a hat with a diaphanous
           veil"; "filmy wings of a moth"; "gauzy clouds of
           dandelion down"; "gossamer cobwebs"; "sheer silk
           stockings"; "transparent chiffon"; "vaporous silks" [syn:
           diaphanous, filmy, gauzy, gauze-like, gossamer,
           see-through, sheer, transparent, vaporous,
           vapourous, cobwebby]

Moby Thesaurus II by Grady Ward, 1.0:

110 Moby Thesaurus words for "filmy":
   attenuate, attenuated, beclouded, blear, bleared, bleary, blurred,
   blurry, clear, clear as crystal, clouded, cloudy, cobwebby,
   confused, crystal, crystal-clear, crystalline, dainty, dark,
   delicate, diaphane, diaphanous, dim, downy, faint, feeble, fine,
   fine-drawn, fine-grained, finespun, flimsy, fluffy, foggy,
   foliaceous, foliated, fuzzy, gauzy, gossamer, gossamery, half-seen,
   half-visible, hazy, ill-defined, in layers, inconspicuous,
   indefinite, indistinct, indistinguishable, insubstantial, lamellar,
   lamellate, lamellated, lamelliform, laminate, laminated, laminous,
   leaflike, leafy, light, light-pervious, limpid, low-profile, lucid,
   membranous, merely glimpsed, milky, misty, murky, nonopaque,
   obscure, opalescent, out of focus, pale, pearly, peekaboo,
   pellucid, pubescent, refined, revealing, satin, satiny, scummy,
   see-through, semivisible, shadowy, sheer, silky, smooth, spathic,
   spathose, stratified, stratiform, thin, thin-spun, three-ply,
   translucent, transparent, transpicuous, two-ply, uncertain,
   unclear, unclouded, undefined, unplain, unrecognizable, vague,
   velutinous, velvety, weak, wiredrawn